Di(het)arylaminothiazole derivatives and their use in organic light-emitting diodes(oleds) and organic photovoltaic components

ABSTRACT

Novel 4,5-di(het)aryl-substituted 2-(N,N-di(het)arylamino)-thiazole derivatives of general structure (a), whereby the following applies: R 1 , R 2 and R 3  and R 4 , independent of one another, are each a monofunctional (het)aryl system; R 1  can additionally be a corresponding bifunctional (het)arylene system; R 3  can additional signify R 7 , whereby R 7  represents a chemical bond or a bifunctional (het)arylene system, or R 3  can be one of the following groupings (b) and (c); R 7  represents a chemical bond or a bifunctional (het)arylene system, and; R 4  can also be H or (d).

[0001] The invention relates to novel di(het)arylaminothiazolederivatives, i.e. diarylaminothiazole or dihetaryl-aminothiazolederivatives (“hetaryl”=“heteroaryl”), and the preparation and usethereof.

[0002] For organic light-emitting diodes (organic LEDs=OLEDs) andorganic photovoltaic components, organic materials which are capable ofelectroluminescence are required. These may be either compounds having asmall molecular size (cf. for example U.S. Pat. No. 4,539,507) which arevaporizable or polymeric materials (cf. for example U.S. Pat. No.5,247,190) which can be processed by spin-coating.

[0003] The synthesis of compounds of said type requires aromaticcoupling reactions. Some of such reactions, in which halogen-containingcompounds are used, take place under metal catalysis, for example by aHeck reaction or by a Suzuki reaction (in this context, cf.: “Chem.Commun.”, 1999, pages 1837 to 1838). However, it is scarcely possible toremove the metal, such as palladium (in this context, cf.: “RömppChemie-Lexikon”, 9th edition, page 1750), completely thereby. However,metals—and also traces of incompletely converted halogen-containingintermediates—act as so-called quenchers, i.e. they quenchelectroluminescence in their environment and they therefore greatlyreduce the efficiency of the materials prepared.

[0004] In an aromatic coupling corresponding to an Ullmann reaction (inthis context, cf.: “Römpp Chemie-Lexikon”, 9th edition, page 4796), theformation of byproducts and of crack products, which are the result ofhigh process temperatures, is a major problem. In fact, the purificationof the reaction product to an acceptable extent is scarcely possiblehere, if at all.

[0005] The invention extends the range of the charge transportmaterials, particularly for the production of charge transport cascades,and is derived from the patent DE 10002424.6.

[0006] The invention therefore relates to novel 4-substituted2-(N,N-di(het)arylamino)thiazole derivatives of the general structure

[0007] in which the following applies:

[0008] R¹, R² and R³—independently of one another—are each amonofunctional (het)aryl system, i.e. a conjugated carbocyclic orheterocyclic ring system, which may also comprise linearly or angularlyfused or linked identical or different ring types, it being possible forthe peripheral hydrogen atoms optionally to be substituted by alkyl,alkoxy, phenoxy, dialkylamino or diphenylamino groups (alkyl=C₁ to C₆);

[0009] the following (het)aryl systems are preferred:

[0010] phenyl, biphenyl, alkylphenyl, alkoxyphenyl, phenoxyphenyl,naphthyl, anthryl, phenanthryl, 4-trityphenyl, thienyl, thiazolyl,benzothiazolyl, pyridyl, quinolyl, isoquinolyl, pyridazinyl,pyrimidinyl, quinazolyl, pyrazinyl, quinoxazyl, phenazinyl and pyrenylsystems.

[0011] R¹ may furthermore be a corresponding bifunctional (het)arylenesystem, i.e. a conjugated carbocyclic or heterocyclic ring system, whichmay also comprise linearly or angularly fused or linked identical ordifferent ring types, it being possible for the peripheral hydrogen atomoptionally to be substituted by alkyl, alkoxy, phenoxy, dialkylamino ordiphenylamino groups (alkyl=C₁ to C₆);

[0012] the following (het)arylene systems are preferred:

[0013] phenylene, biphenylene, alkylphenylene, alkoxyphenylene,phenoxyphenylene, napthylene, anthrylene, phenanthrylene, thienylene,thiazolylene, pyridazinylene, phthalazinylene and pyrazinylene systems.

[0014] R¹ and R2 together may also form a 10-phenothiazinyl,10-phenoxazinyl or 9-carbazolyl group.

[0015] R³ may furthermore be R⁷, R⁷ being a chemical bond or abifunctional (het)arylene system, or R³ may be one of the followinggroups:

[0016] R⁷ being a chemical bond or a bifunctional (het)arylene system;

[0017] R⁴ may also be H or

[0018] the following may furthermore be the case:

[0019] R³ and R⁴ together form one of the following groups:

[0020] R³ together with R¹ forms the following polymer segment:

[0021] R⁴ together with R¹ forms the following polymer segment:

[0022] R⁴ and R³ together with R¹ form the following polymer segments:

[0023] Y in each case being CH or N.

[0024] The preparation of the novel di(het)arylaminothiazole derivativesis effected by means of a hetaryl cyclization reaction under mildconditions and without metal catalysts. These compounds can thus beprepared in high purity, i.e. the efficiency of these materials, inparticular the electroluminescence, is not adversely affected byimpurities which are present in compounds prepared by known processes,for example owing to the catalyst used. A further advantage of thesematerials consists in improved redox properties adaptable to therespective purpose and due to the variety of structural possibilitieswhich arises from the structural principle described in more detailbelow. This structural principle furthermore enables the novel materialsto be obtained without problems also in the form of oligomer and polymerstructures, i.e. for oligo- and polyaminothiazole derivatives to beprepared, and the maximum degree of polymerization of n=100 cannot beexceeded owing to the stepwise condensation.

[0025] The synthesis of the novel compounds requires in some casesprecursors which have been unknown to date. However, these precursorsare obtainable—from commercially available starting materials—invirtually quantitative yield.

[0026] Preparation of the thiourea starting materials:

[0027] Preparation of the thiazole derivatives:

[0028] The following applies here:

[0029] R¹, R², R³ and R⁴ have the abovementioned meanings;

[0030] R⁵ and R⁶—independently of one another—are each a monofunctional(het)aryl system, i.e. a conjugated carbocyclic or heterocyclic ringsystem, which may also comprise linearly or angularly fused or linkedidentical or different ring types, it being possible for the peripheralhydrogen atoms optionally to be substituted by alkyl, alkoxy, phenoxy,dialkylamino or diphenylamino groups (alkyl=C₁ to C₆);

[0031] R⁵ may furthermore be the group R⁸, the compound V carrying agroup —CO—CH₂X, where X is halogen, preferably Cl, Br or I, at the freebond,

[0032] or R⁵ may be a group —C(CO—CH₂X)₃.

[0033] R⁶ may also be hydrogen.

[0034] The first stage of the synthesis of the thiazole derivativescomprises the reaction of a secondary amine I with pivaloylisothiocyanate II to give an N,N-disubstituted pivaloylthiourea III. Thereaction is carried out in a suitable solvent, preferably acetone, atelevated temperature, preferably in the region of the boiling point ofthe solvent, under inert gas. As a rule, the product need not beisolated and is then converted, in a second stage, in aqueoushydrochloric acid, into the N,N-disubstituted thiourea IV.

[0035] In a third stage, the N,N-disubstituted thiourea IV—depending onthe substitution pattern (cf. IVa and IVb below)—is converted byreaction with an α-haloacyl compound V in a suitable solvent, preferablyacetic anhydride, dimethylformamide or ethanol, into a semiconducting4-substituted 2-(N,N-di(het)arylamino)-thiazole derivative VI, accordingto the substitution pattern of the acyl compound (cf. Vb to Vd below).This is effected by a primary S-alkylation and a subsequent cyclization(ring closure reaction) and aromatization according to the “Hantzthiazole synthesis”. Cyclization can also be accelerated by adding adeprotonating agent, preferably triethylamine.

[0036] Thiazole derivatives VI which are unsubstituted in the5-position, i.e. R⁴=H, can be converted by oxidative coupling intodimeric or polymeric derivatives VI (cf. VIe, f, i, m, n, p, s below),which are likewise organic semiconductor materials. The oxidativecoupling is effected in a suitable solvent, preferably drytetrahydrofuran, by oxidizing agents known per se, preferably byoxidation of the respective lithium-complexed thiazolederivative—prepared by means of butyllithium—with copper(II) chloride orby electrooxidation on a conductive substrate, for example on a glasssheet coated with ITO (ITO=indium tin oxide)

[0037] By means of halogenated 1,2-diketones (cf. Vd/d below)—as anα-haloacyl compound—thiazole derivatives VI prepared from the thioureasIV and unsubstituted in the 5,5′-position and bonded in the4,4′-position (cf. VIq and VIr below) can be converted with orthoformicester or with nitrous acid, which is generated, for example, from sodiumnitrite or isoamyl nitrite, into corresponding cationic hole transportmaterials (cf. VIt and VIu below), which are similar to the knownpolythiophenes and polyanilines in their properties as organicconductors.

[0038] The structural formulae of a relatively large number of the novelthiazole derivatives—together with the direct starting materials—arereproduced in the form of a table below. Organic semiconducting productsfrom the combinations of thioureas IV and □-haloacyl compounds V andtheir oxidation products and conductive cationic structures

   Oxidation

[0039] R⁶ is an alkyl radical having 1 to 5 C atoms,

[0040] Z⁻ is any desired anion, preferably a polystyrenesulfonate oranother organic sulfonate,

[0041] n is in each case an integer from 2 to 100, on average a degreeof polymerization n=20 to n=40 being reached.

[0042] The thiazole derivatives according to the invention of type VIare all suitable materials for the production of organic light-emittingdiodes (OLEDs) and organic photovoltaic components or cells. They can beused both in hole transport layers or layer cascades and in emitter andelectron transport layers. The respective layer position in OLEDs isdetermined in particular by the (het)aryl or (het)arylene members: themore of these members which have a π-electron deficiency, i.e. so-calledπ-deficient aromatics, the more suitable are the thiazole derivatives asemitter and electron transport materials.

[0043] The following compound types are particularly preferred:—VIb,VId, VIe, VIf, VIg, VIm, VIp, VIt and VIu.

[0044] OLED materials which are suitable as vaporizable compounds forso-called “small molecule devices” and polymer materials processible byspin-coating and intended for so-called “polymer devices” can berealized by the synthesis route described; the nonpolymeric materialscan likewise be processed by spin-coating. Owing to the common parentstructure of all the materials, corresponding copolymers having tailoredelectronic properties can also advantageously be prepared. It isfurthermore possible to realize the electronic properties required forthe respective intended use by means of mixtures of correspondingmaterials, which—owing to the structural similarity—are very compatiblewith one another. Materials tailored in this manner therefore permit asingle-layer structure of OLEDs, which is very advantageous. By theadditional use of the materials described in the patents DE 10002423.8and DE 10002424.6 for optimum charge transport cascades, it is possibleto realize OLEDs having a lower operating voltage (onset 2.5-3 V). Alsonoteworthy are the glass transition temperatures of the charge transportand emitter materials prepared in the manner described, whichtemperatures are very high compared with known carbocyclic chargetransport materials and are in general from about 50 to 100° C. higherthan those of the analogous carbocyclic compounds which, withexceptions, have a glass transition temperature of from 100° C. to 150°C. The thiazole derivatives according to the invention have a glasstransition temperature of at least 180° C., preferably of at least 200°C., in particular in the range from 230 to 250° C.

[0045] The invention is to be explained in more detail with reference toembodiments.

EXAMPLE 1 Synthesis of the Pivaloylthioureas III

[0046] 1 mol of potassium thiocyanate in 500 ml of absolute acetone isinitially introduced into a 2 l three-necked flask having a refluxcondenser, a magnetic stirrer, dropping funnel and inlet gas flow, and 1mol of pivaloyl chloride is added dropwise. Thereafter, refluxing iseffected for one hour and the respective equivalent amount of thecorresponding secondary amine I (monofunctional 1 mol, bifunctional 0.5mol), dissolved or suspended in 300 ml of acetone, is then addeddropwise. The reaction mixture is then refluxed until amine is no longerdetectable by thin-layer chromatography. The reaction solution is thencooled and is stirred into at least twice the amount of dilute, aqueoushydrochloric acid. The aqueous phase is separated off and discarded, andthe crude product can be immediately further processed.N,N′-Diphenyl-N,N′-di(thioform-pivaloylamido)-1,4-phen-ylenediaminehaving a melting point of 165° C. is prepared in this manner, forexample from N,N′-diphenyl-1,4-phenylenediamine, pivaloyl chloride andpotassium thiocyanate.

EXAMPLE 2 Synthesis of N,N-Disubstituted Thioureas IV

[0047] The corresponding pivaloylthiourea are suspended in conc.hydrochloric acid in a beaker. 400 ml of conc. hydrochloric acid shouldbe metered for 1 mol of pivaloyl group to be eliminated. The reactionmixture is heated to the boil until the resulting frothing has ended. Itis then poured onto ice, the product separating out. The product isfiltered off with suction and is recrystallized from ethanol.

[0048] The yield in each case is at least 80%.

[0049] For example, the thiourea IVa (R¹=R²=phenyl) having a meltingpoint of 212° C. is prepared in this manner.

EXAMPLE 3 Synthesis of Thiazole Derivatives VI

[0050] a)

[0051] 0.1 mol of the respective N,N-disubstituted thiourea IV aredissolved, together with an equivalent amount of an α-haloacyl compoundV, in 200 ml of DMF in a flask provided with a stirrer and refluxcondenser, after which heating is effected at 100° C. for 1 h.Thereafter, 0.1 mol of triethylamine are added and heating is effectedfor a further 30 min. After cooling, the thiazole derivative formed isisolated by precipitating with methanol, in some cases also with icewater, and filtering off with suction. The crude product is purified byrecrystallization from ethanol. The yield in each case is from 60 to80%.

[0052] For example, the thiazole derivative VIb (R¹=1,4-phenylene andR²=R³=R⁴=phenyl) is prepared from the bifunctional thiourea IVb(R¹=1,4-phenylene and R²=phenyl) and desyl chloride(α-chloro-α-phenylacetophenone) in this manner.

[0053] m.p.=300° C., MS: MH⁺=731, T(g) =240° C. ¹H-NMR: (DMF-D₇

[0054] a) 7.65 ppm (s) 4H

[0055] b) 7.35 ppm (d) 4H

[0056] c) 7.62 ppm (d) 4H

[0057] b)

[0058] The following procedure is adopted for the preparation ofpolymeric thiazole derivatives VI, for example VIf (R¹=1,4-phenylene andR²=R³=phenyl):

[0059] 0.1 mol of bifunctional thiourea IVb (R¹=1,4-phenylene,R²=phenyl) are dissolved, together with 0.1 mol of dimeric phenacylbromide Vc (R²=phenyl), in 200 ml of DMF in a flask provided with astirrer and reflux condenser, after which heating is effected at 100° C.for 1 h. Thereafter—for capping the end groups—a monofunctional thioureaIVa and a monofunctional acyl halide Va are added in succession, in thepresent case first 0.01 mol of N,N-diphenylthiourea and after 60 min0.01 mol of phenacryl bromide. After a further 60 min, 0.1 mol oftriethylamine are added and the mixture is allowed to cool after afurther 15 min, the polymeric thiazole derivative formed beingprecipitated. The further working-up is effected in the manner describedabove; yield: about 80%.

[0060]¹H-NMR: (DMF-D₇

[0061] c) 7.1 ppm (s) 4H

[0062] d) 6.9 ppm (t) 2H

[0063] c) 7.3 ppm (t) 2H

EXAMPLE 4 Synthesis of Dimeric or Polymeric Thiazole Derivatives VI (byOxidative Coupling)

[0064] 0.01 mol of a thiazole derivative VI unsubstituted in the5-position are dissolved in 100 ml of dried THF in a flask provided witha reflux condenser, stirrer, solids metering means and inert gas flow.The mixture is cooled to −60° C., after which 0.015 mol of butyllithiumare added. Thereafter, the cooling is removed and the reaction mixtureis allowed to thaw to −10° C. Thereafter, 0.011 mol of copper(II)chloride are added by the solids metering means, and heating is thencontinued up to 40° C. The reaction is stopped after 30 min byprecipitating the product with water (in the case of polymers, withmethanol with addition of 10% of water) and then filtering it off withsuction. The product is purified with repeated dissolution in THF andprecipitation with methanol. Nonpolymeric compounds can also be purifiedby sublimation.

[0065] For example, the dimeric thiazole derivative VIe(R¹=R²=R³=phenyl) is prepared from 2-diphenylamino-4-phenylthiazole VIcin this manner. M.p.: 255-258° C., MS: MH+=655, and the polymer VIfalready prepared in example 3b.

[0066]¹H-NMR: (CDCl₃)

[0067] a) 7.21 ppm (d) 8H

[0068] b) 7.68 ppm (d) 4H

EXAMPLE 5 Synthesis of Thiazole Derivatives VI in the Form ofCationically Conductive Materials (Y=CH)

[0069] 0.01 mol of a dimeric thiazole derivative VIq or VIr bonded inthe 4,4′-position and unsubstituted in the 5,5′-position are dissolvedin 100 ml of DMF in a beaker, and 0.015 mol of triethyl orthoformate isadded. After the addition of 0.01 mol of perchloric acid and heating toabout 100° C., a dye salt which absorbs in the long-wave range forms,which salt is precipitated after the addition of ethanol and possibly alittle ether and is then filtered off with suction. By reaction of thedye perchlorate with a solution of sodium polystyrenesulfonate, anaqueous solution of the respective cationically conductive material isobtained in the form of polystyrenesulfonate; this solution can beprocessed by spin-coating.

[0070] For example, the thiazole derivative VIt (R¹=R²=phenyl and Y=CH)is prepared from the thiazole derivative VIq (R¹=R²=phenyl) and triethylorthoformate in the presence of perchloric acid in this manner.

[0071] NMR: (DMF-D⁷):

[0072] a) 7.66 ppm (s) 1H

[0073] b) 7.77 ppm (t) 4H

EXAMPLE 6 Synthesis of Thiazole Derivatives VI in the Form ofCationically Conductive Materials (Y=N)

[0074] 0.01 mol of a dimeric thiazole derivative VIq or VIr bonded inthe 4,4′-position and unsubstituted in the 5,5′-position are dissolvedin 100 ml of THF in a beaker, and 0.015 mol of isoamyl nitrite is added.After the addition of 0.01 mol of perchloric acid with cooling andsubsequent heating to about 50° C., a dye salt which absorbs in thelong-wave range forms, which salt is precipitated after the addition ofethanol and possibly a little ether and is then filtered off withsuction. By reacting the dye perchlorate with a solution of sodiumpolystyrenesulfonate, an aqueous solution of the respective cationicallyconductive material is obtained in the form of the polystyrenesulfonate;this solution can be processed by spin-coating.

[0075] For example, the thiazole derivative VIt (R¹=R²=phenyl and Y=N)is prepared from the thiazole derivative VIq (R¹=R²=phenyl) and isoamylnitrite in the presence of perchloric acid in this manner.

[0076] NMR: (DMF-D₇):

[0077] a) 7.66 ppm (s) 1H

1. A 4-substituted 2-(N,N-di(het)arylamino)thiazole derivative of thegeneral structure

in which the following applies: R¹, R² and R³—independently of oneanother—are each a monofunctional (het)aryl system, i.e. a conjugatedcarbocyclic or heterocyclic ring system, which may also compriselinearly or angularly fused or linked identical or different ring types,it being possible for the peripheral hydrogen atoms optionally to besubstituted by alkyl, alkoxy, phenoxy, dialkylamino or diphenylaminogroups (alkyl=C₁ to C₆); R¹ may furthermore be a correspondingbifunctional (het)arylene system, i.e. a conjugated carbocyclic orheterocyclic ring system, which may also comprise linearly or angularlyfused or linked identical or different ring types, it being possible forthe peripheral hydrogen atoms optionally to be substituted by alkyl,alkoxy, phenoxy, dialkylamino or diphenylamino groups (alkyl=C₁ to C6);R³ may furthermore be R⁷, R⁷ being a chemical bond or a bifunctional(het)arylene system, or R³ may be one of the following groups:

R⁷ being a chemical bond or a bifunctional (het)arylene system; R⁴ mayalso be H or

the following may furthermore be the case: R³ and R⁴ together form oneof the following groups:

R³ together with R¹ forms the following polymer segment:

R⁴ together with R¹ forms the following polymer segment:

R⁴ and R³ together with R¹ form the following polymer segments:

Y in each case being CH or N.
 2. The thiazole derivative as claimed inclaim 1, having the following structure:


3. The thiazole derivative as claimed in claim 1, having the followingstructure:


4. The thiazole derivative as claimed in claim 1, having the followingstructure:


5. The thiazole derivative as claimed in claim 1, having the followingstructure:

Z⁻ being an anion, Y being —CH═ or —NH═ and n being an integer from 2 to100.
 6. The thiazole derivative as claimed in claim 1, having thefollowing structure:

n being an integer from 2 to
 100. 7. A process for the preparation of athiazole derivative as claimed in claim 1, characterized by thefollowing steps: (a) reaction of a secondary amine with a pivaloylisothiocyanate to give a pivaloylthiourea; (b) conversion of thepivaloylthiourea into a thiourea; (c) reaction of the thiourea with a(het)aryl-substituted α-haloacyl compound to give a2-(N,N-di(het)arylamino)-4-(het)arylthiazole derivative or a2-(N,N-di(het)arylamino)-4,5-di(het)arylthiazole derivative.
 8. Theprocess as claimed in claim 7, characterized in that the2-(N,N-di(het)arylamino)-4-(het)arylthiazole derivative is convertedoxidatively into a dimer or polymer.
 9. The process as claimed in claim7, characterized in that the 4,4′-bisthiazolyl derivatives (VIg and VIr)are converted into heterocyclic, cationic polymethines orpolyazamethines (VIt and VIu) by means of orthoformic esters or nitrousacid.
 10. The use of a thiazole derivative as claimed in any of claims 1to 6 in organic light-emitting diodes.
 11. The use of a thiazolederivative as claimed in any of claims 1 to 6 in organic photovoltaiccomponents.
 12. An organic light-emitting diode which comprises at leastone thiazole derivative as claimed in any of claims 1 to 6 as a chargetransport layer and/or emitter layer, the electronic properties of the(het)aryl substituent determining whether the thiazole derivative haselectron-transporting or hole-transporting activity.
 13. The thiazolederivative as claimed in claim 1, having a glass transition temperature(Tg) of at least 180° C.